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Querying Data

This topic provides information about using SQL in Greenplum databases.

You enter SQL statements called queries to view, change, and analyze data in a database using the psql interactive SQL client and other client tools.

  • About Greenplum Query Processing

    This topic provides an overview of how Greenplum Database processes queries. Understanding this process can be useful when writing and tuning queries.

  • About GPORCA

    In Greenplum Database, the default GPORCA optimizer co-exists with the Postgres Planner.

  • Defining Queries

    Greenplum Database is based on the PostgreSQL implementation of the SQL standard.

  • WITH Queries (Common Table Expressions)

    The WITH clause provides a way to use subqueries or perform a data modifying operation in a larger SELECT query. You can also use the WITH clause in an INSERT, UPDATE, or DELETE command.

  • Using Functions and Operators

    Description of user-defined and built-in functions and operators in Greenplum Database.

  • Working with JSON Data

    Greenplum Database supports the json and jsonb data types that store JSON (JavaScript Object Notation) data.

  • Working with XML Data

    Greenplum Database supports the xml data type that stores XML data.

  • Using Full Text Search

    Greenplum Database provides data types, functions, operators, index types, and configurations for querying natural language documents.

  • Using Greenplum MapReduce

    MapReduce is a programming model developed by Google for processing and generating large data sets on an array of commodity servers. Greenplum MapReduce allows programmers who are familiar with the MapReduce model to write map and reduce functions and submit them to the Greenplum Database parallel engine for processing.

  • Query Performance

    Greenplum Database dynamically eliminates irrelevant partitions in a table and optimally allocates memory for different operators in a query.

  • Managing Spill Files Generated by Queries

    Greenplum Database creates spill files, also known as workfiles, on disk if it does not have sufficient memory to run an SQL query in memory.

  • Query Profiling

    Examine the query plans of poorly performing queries to identify possible performance tuning opportunities.